Project Summary/Abstract The high incidence of post-surgical fibrosis is no trivial feat for a pediatric gynecologist such as myself who is among the the few specialists trained to perform intricate vaginal reconstruction surgeries. What is strikingly perplexing is that, unlike dermal tissues, oral, gastrointestinal, and vaginal mucosa are programmed to heal regeneratively and without scarring. Yet, there are no scientifically tailored clinical strategies to prevent or at least treat vaginal fibrosis, which currently rely on the application of tissue stretch with rudimentary dilators or stents and local treatment with pre- and post-operative estrogen. The inevitable result is high morbidity, increased health care costs, and significant reduction in quality of life for adolescent and adult female patients that had just endured the trauma of vaginal surgery, injury, or pelvic radiation. I plan to use this K08 award to develop myself as one of a few pediatric gynecological surgeon-scientists and use this platform to understand what directs vaginal mucosal tissue into regenerative or fibrotic repair. While I acknowledge the gap of knowledge, I also recognize that the key to decipher the dichotomy of tissue regeneration and fibrosis lies with the ubiquitous extracellular matrix (ECM) signaling, particularly through proteoglycans such as hyaluronan via a specific receptor. In particular, hyaluronan (HA) is known to impact wound healing through its high affinity receptor CD44, where the latter engages in inflammatory reactions upon HA binding. Remarkably, pro- inflammatory low and anti-inflammatory high molecular weight (LMW/HMW) HA variants are synthesized upon injury, which led me to query whether estrogen levels play any role to modulate how ECM directs HA/CD44 signaling in the vaginal mucosa. Notably, my preliminary data show that fibrosis can be attenuated by combined estrogen and hyaluronan (HA) controlled release delivery, where the combined protective effect against fibrosis was upheld by enhanced anti-inflammatory and pro-angiogenic reactions. Through testing of stents with different material properties, these studies also unveiled a critical threshold of tissue stretch that contributes to regenerative repair and suggest that HA and estrogen are essential mediators of these effects. However, the missing link is that the mechanisms that transduce estrogen-driven HA/CD44 signaling to direct mucosal repair remain unknown. Hence, my overarching hypothesis is that the direction of vaginal wound repair is governed by estrogen-driven signals transduced via HA ligand/CD44 receptor interactions that respond to tension. Thus, I aim to: (i) Investigate the role of estrogen on the regulation of HA biology in vaginal tissue repair; (ii) Study how estrogen drives CD44 signaling-mediated vaginal inflammation and influences regenerative tissue repair; and (iii) Test whether regulating the estrogen-HA-axis can improve wound repair. At the end of this K08 award, I will have acquired the necessary skills and knowledge to become an independent investigator, pursue a career as a surgeon-scientist, and lead the field of mucosal regeneration.